This invention relates in general to the field of containers for transporting and dispensing pre-stored heat to balls used in impact sports, e.g. golf balls, at a temperature elevated above ambient during play, and more particularly to such containers which use "phase change materials" (as defined below) for storing latent heat of fusion and subsequently dispensing same to the balls by undergoing a phase change.
Golf balls are designed to achieve maximum flight distances when struck by a golf club. It has been found that the temperature of a golf ball affects its ability to rebound from a club face. In other words, the temperature of a ball affects the distance it travels, and increased flight distances can be achieved by heating a golf ball to elevated temperatures. For example, if a given impact force would carry a golf ball at 75.degree. Fahrenheit (F) 220 yards, the same impact could be expected to carry a golf ball at 105.degree. F. about 226 yards. This is an increase of six yards as a result of the higher temperature.
While the rules of the Professional Golfing Association (PGA) do not prevent a golfer from using a heated golf ball, it is impossible to keep a ball warm while it is in play. And even if a golfer starts out with a plurality of heated golf balls to replace those that get cold, it would be very difficult to maintain a set of balls at an elevated temperature over the course of eighteen holes. Even heated balls carried in a container having walls of one-half inch thick polyurethane foam insulation will rapidly lose their heat, generally within an hour.
The desire to play with heated golf balls has fostered a variety of methods and devices for heating balls on the course, for example: using the exhaust of a gasoline powered golf cart; using resistance heating powered by a golf cart's battery; using resistance heating powered by a portable battery; using hot air circulating from a cart's heater; and non-rechargeable, chemically activated, heating elements. These methods all require that heat sources be carried or stationed around a course, and it is against PGA rules to use a handwarmer or other device for the purpose of heating a ball during play.
This invention solves the above-described problems. This invention provides a ball caddy for transporting a plurality of pre-heated balls which drastically reduces heat loss such that golf balls contained therein can be kept at a significantly elevated temperature even during the time it takes to play eighteen holes, thus enabling a golfer to start each hole with a heated golf ball. The caddy is insulated and includes a ball pouch which has reusable, environmentally safe, phase change material ("PCM") incorporated in its walls.
Phase change material or PCM derives its name from its ability to absorb, or release, substantial amounts of heat at a relatively constant temperature during changes in phase, such as when it changes from a solid to a liquid, or from a liquid to a solid, respectively. The amount of heat a PCM must absorb to change from a solid to a liquid, or release to change from a liquid to a solid, is called the its latent heat of fusion which is substantially greater than the sensible heat capacity of the material. While most materials generally absorb or give up heat linearly with a rise or decrease, respectively, in the surrounding temperature, this is not true when a change in phase occurs. For example, to change a material from a solid phase to a liquid phase, a considerable amount of heat, its latent heat of fusion, must be added to the material. While heat is being added to the material its temperature will rise generally proportionally to the rate at which heat is being added. However once the temperature of the solid reaches its melting, or phase change point, its temperature will not change significantly so long as any of the material remains solid. Only after generally all the material has melted, i.e. changed into its liquid phase, will the temperature of the material again start to rise generally linearly with the absorption of additional heat.
Likewise, a liquid material will radiate or give up heat as it cools, but once it reaches its freezing temperature, the temperature of the material will not significantly change until all of the material has frozen. i.e. changed in phase to a solid. (As used in this document, the term "freezing temperature" does not necessarily refer to the freezing temperature of water, but rather shall mean a temperature at which a subject material changes phase from a liquid to a solid.) In other words, the material will remain generally at its freezing temperature until it has lost its latent heat of fusion, at which point all the liquid has changed to its solid phase.
U.S. Pat. No. 5,211,949 by Salyer describes PCM combinations that are dry powder mixes above and below the phase change temperature of the PCM, and PCM gels. It also discloses use of waxes as PCMs.
The PCM mix used in this invention can be in powder or gel form, and can also be compounded to have usable freezing temperatures in a wide range above a comfortable outdoor ambient temperature. PCM is well suited for this application because upon heating or freezing, per weight, a PCM absorbs or releases substantially more energy than a sensible heat storage material which is heated or cooled to the same temperature range. In addition to their latent heat storage capacity, the PCMs of this invention also store and release sensible heat. Thus the latent storage is augmented to a significant extent by the PCMs' sensible heat storage capacity.
Also, extreme cold adversely affects carry distance for all constructions of golf balls. The feel of the ball becomes dramatically harder. This invention can be used to prevent even unheated balls from cooling to ambient temperature when it is adversely low.
Other advantages and attributes of this invention will be readily discernable upon a reading of the text hereinafter.